The subject of the present invention is a latch, mainly intended for the closure of a section door or the like. The invention also concerns some operating sets and an assembly, including said latch.
The section doors are used mainly in the garages and the like, and they are formed by a number of sections in the shape of horizontally elongated elements, each connected to the adjacent ones by hinges, composing in their whole a rolling shutter which slides on side guide bars. In order to attain a quick running movement, near the hinges located between the shutter elements there are provided, at both ends of the shutter elements, small rolling wheels which turn on horizontal pivots or axles and roll within the side guide bars. Each side guide bar has a vertical branch which defines the operative position of the section door when closed, a upper horizontal branch which defines a disappearance position of the section door when open, and a curved connection branch joining together said vertical and horizontal branches.
Some section doors are moved by a powered mechanism controlled by a key or a remote control, and this mechanism in general is irreversible or is hardly reversible, whereby it opposes by itself to any opening attempt not controlled by the motor. Therefore, the presence of other means suitable for blocking the door would not be unavoidable; nevertheless, in most cases such doors are also provided with a side latch intended for engaging, in its active position, in an opening provided in one of the side guide bars, and this latch may be manually operated or a handle lock may be provided for operating the latch. The provision of the latch may be bilateral. In any event, the provision of at least one latch, and often of a handle lock too, is needed in those cases in which the section door is not motor operated.
The section doors suffer a serious problem with reference to the latches. Usually, the latches are located in a more or less middle position along the height of an element of the section door, and they should have a very long stroke which comprises, in addition to the normal operating stroke of any latch with respect to the opening with which it should engage, by taking into account the lateral play foreseen for the elements, also the stroke needed for displacing the latch out of the thickness of the corresponding side guide bar. This is needed in order that the latch may go beyond the curved connection branch without interfering with the guide bar. As a consequence, the stroke needed for these latches may amount, in general, to about 50 millimeters, and it is very larger than the usual stroke of a latch, which is in general of about 25 millimeters; this is the stroke along which a latch is usually operated manually, and which can be easily operated by a lock handle.
Therefore, when the latch is operated manually, the user should take care of operating the latch along its entire, unusually long stroke because, if inadvertently he opens the latch only in part, then a clamping or even a serious damage of the section door takes place during the door opening. On the other hand if, as it often happens, the latch is operated by a handle lock, it is necessary to use a handle mechanism having features suitable to cover a long stroke, but such features are unusual for such mechanisms and, moreover, they are difficult to be embodied and are not of handy maneuver.
Operating such a long latch stroke through a limited rotation angle of a handle would be of difficult realization and, in any event, would require an excessive effort. The longer stroke could be obtained by imposing to the user a handle rotation more extended than the usual one of 90°, and this stroke should be obtained by rotating the handle in two subsequent times separated by a momentary abandonment of the handle. Such maneuver is uncomfortable, but in addition thereto it involves the danger that the user inadvertently omits the second part of the stroke whereby the latches, abandoned at a half of their stroke, come then to interfere with the guide bars in correspondence of the curved connection branches, thus causing the clamping or a serious damage of the section door.
An attempt has been made to make up for this dangerous disadvantage by submitting the handle to the action of a strong return spring, which impedes to abandon the handle in an intermediate position. However, in this case the maneuver of the handle should overcome, in addition to the resistance of the latch movement, the force of the spring, whereby the maneuver involves an excessive effort and is very uncomfortable.
Another disadvantage shown by the section doors is that it is very difficult to provide an automatic closure of the latches when the closure position is attained by the section door; this effect may be obtained only at the cost of serious constructive complications. However, this automatic closure would be very desirable for the users.